1. Field of the Invention
The present invention relates to a piston machine for delivering of gases, including a cylindrical wall defining a swept volume and having a plurality of gas inlet openings, a gas outlet valve, and a piston reciprocating in the swept volume and having a piston head.
2. Description of the Prior Art
Piston machines of the types described above are used, among others, in vacuum technology for delivery of gases and for generating and maintaining of a pressure difference, i.e., as vacuum pumps. A vacuum pump of this type is disclosed, e.g., in U.S. Pat. No. 5,921,755.
The present invention relates to one- or multi-stage constructions. In the piston machines of the above-described type, the piston reciprocates between the two dead points. During a return stroke of the piston, the gas is compressed and is expelled. During the return stroke, underpressure or vacuum is formed in the swept volume. As a result, the gases can flow into the swept volume through a suitable valve.
The work, which is produced during the return stroke of the piston is a result of a pressure difference between the pressure in the operational volume (space) of the piston and an underpressure in the swept volume (space). This work also depends on the surface of the piston (its size) and on the stroke length. The work produced during the return stroke of the piston increase the power consumption of the piston drive and leads to heating of the machine (pump) components, which adversely affect the operation of the machine and leads to increased friction losses. The removal of heat requires additional, undesirable expenses.
Accordingly, an object of the invention is to provide a piston machine in which an additional, unnecessary energy consumption and an undesirable heating of the machine components are eliminated.
Another object of the present invention is to provide a piston machine in which no dead volume is formed in the region of the pump active components (e.g., the piston, valves), which dead volume noticeably adversely affects the machine characteristics during the gas pumping process.